From a viewpoint of improving the yield in fabrication of semiconductor devices, management of surface conditions of a peripheral portion of a substrate has been attracting attention in recent years. In the fabrication process of the semiconductor devices, various materials are deposited on a silicon wafer. As a result, unwanted films and rough surfaces are formed on a peripheral portion of the substrate. It has been a recent trend to transport the substrate by holding only its peripheral portion using arms. Under such circumstances, the unwanted films remaining on the peripheral portion may peel off during various processes and may adhere to devices formed on the substrate, thus decreasing the yield. Thus, in order to remove the unwanted films formed on the peripheral of the substrate, the peripheral portion of the substrate is polished using a polishing apparatus.
This type of polishing apparatus polishes the peripheral portion of the substrate by bringing a polishing surface of a polishing tape into sliding contact with the peripheral portion of the substrate. In this specification, the peripheral portion is defined as a region including a bevel portion which is the outermost portion of the substrate and a top edge portion and bottom edge portion located on the inner side in the radial direction of the bevel portion.
FIGS. 1A and 1B are enlarged cross-sectional views each illustrating a peripheral portion of a substrate W. More specifically, FIG. 1A illustrates a cross-sectional view of a so-called straight-type substrate, and FIG. 1B illustrates a cross-sectional view of a so-called round-type substrate. In the substrate W illustrated in FIG. 1A, the bevel portion is an outermost circumferential surface of the substrate W (indicated by symbol B) that is constituted by an upper slope (an upper bevel portion) P, a lower slope (a lower bevel portion) Q, and a side portion (an apex) R. In the substrate W illustrated in FIG. 1B, the bevel portion is a portion B having a curved cross-section and forming an outermost circumferential surface of the substrate W. The top edge portion is a flat portion E1 located on the inner side in a radial direction of the bevel portion B and located on the outer side in the radial direction of a region D where devices are formed. The bottom edge portion is a flat portion E2 located opposite to the top edge portion and located on the inner side in the radial direction of the bevel portion B. These top edge portion E1 and bottom edge portion E2 may be collectively referred to as near-edge portions.
A conventional polishing apparatus (for example, see JP 2012-213849A) that polishes a peripheral portion of a substrate by pressing a polishing tape against the peripheral portion of the substrate includes a substrate holder configured to hold and rotate a substrate and at least one polishing unit configured to polish the peripheral portion of the substrate. This polishing unit includes a polishing head having a pressing member configured to press a polishing tape against the peripheral portion of the substrate from above, and a tape supply and recovery mechanism configured to supply the polishing tape to the polishing head and to recover the polishing tape from the polishing head. The polishing head can move in a radial direction of the substrate with the aid of a first moving mechanism, and the tape supply and recovery mechanism can move in the radial direction of the substrate with the aid of a second moving mechanism. The tape supply and recovery mechanism has a plurality of guide rollers for supporting the polishing tape, and the plurality of guide rollers are arranged such that the polishing tape extends in parallel to a tangential direction of the substrate and a polishing surface of the polishing tape is in parallel to a surface of the substrate. During polishing, liquid (for example, pure water) is supplied to the center of the rotating substrate so that the substrate is polished in the presence of the water. The liquid supplied to the substrate spreads over the entire upper surface of the substrate by a centrifugal force.
The polishing tape is a long and narrow strip-shaped polishing tool. Although a width of the polishing tape is basically constant throughout its entire length, there may be a slight variation in the width of the polishing tape in some parts thereof. Therefore, whenever the polishing tape is sent by the tape supply and recovery mechanism to provide a new polishing surface under the pressing member, the position of the edge of the polishing tape at the polishing position where the polishing tape is pressed against the pressing member may vary. Thus, the polishing apparatus includes a polishing tape-edge detection sensor that detects the position of an edge of the polishing tape in order to align the edge of the polishing tape with the edge of the pressing member.
FIGS. 2A to 2C are views illustrating an operation of detecting the edge of a polishing tape 38 using a tape-edge detection sensor 100. Prior to polishing of a substrate W, the polishing tape 38 supported on a tape supply and recovery mechanism 70 is moved from a retracted position illustrated in FIG. 2A to a tape-edge detecting position illustrated in FIG. 2B. In this tape-edge detecting position, the position of the substrate-side edge of the polishing tape 38 is detected by the tape-edge detection sensor 100. This tape-edge detection sensor 100 is a transmission optical sensor. The tape-edge detection sensor 100 has a light emitter 100A and a light receiver 100B. This tape-edge detection sensor 100 is configured to emit light from the light emitter 100A to the light receiver 100B and to detect the position of the edge of the polishing tape 38 based on a quantity of the light received by the light receiver 100B. After that, as illustrated in FIG. 2C, the polishing tape 38 is moved to a polishing position by the second moving mechanism so that the edge of the polishing tape 38 coincides with the edge of a pressing member 51.
As described above, although liquid is supplied to the center of the rotating substrate W during polishing and the liquid spreads over the entire upper surface of the substrate W by a centrifugal force, the liquid may become water droplets which may adhere to the polishing tape 38. Thus, when water droplets adhere to the edge portion, in particular, of the polishing tape 38, the light projected from the light transmitter 100A of the tape-edge detection sensor 100 may scatter by the water droplets, and as a result, the light that is to enter the light receiver 100B may not enter the light receiver 100B correctly. Thus, it is difficult to detect the edge of the polishing tape 38 accurately using the tape-edge detection sensor 100 and the positional accuracy of the polishing tape 38 decreases. Moreover, in order to prevent a decrease in the positional accuracy caused by such water droplets, it is necessary to remove the water droplets using air nozzle or the like so that water droplets do not adhere to the polishing tape 38. As a result, the apparatus configuration becomes complex.
With the foregoing in view, an object of the present application is to provide a polishing apparatus capable of positioning the polishing tape with high accuracy.
According to an embodiment, there is provided a polishing apparatus including: at least one polishing unit configured to polish an edge portion of a substrate; and a positioning unit, wherein the polishing unit includes: a polishing head having a pressing member configured to absorb a polishing tape and press the polishing tape against a peripheral portion of the substrate from above; a tape supply and recovery mechanism configured to supply the polishing tape to the polishing head and recover the polishing tape from the polishing head; a first moving mechanism configured to move the polishing head in a radial direction of the substrate; and a second moving mechanism configured to move the tape supply and recovery mechanism in the radial direction of the substrate, the positioning unit includes a positioning block having a contacting surface, and alignment of the polishing tape is conducted by the second moving mechanism moving the tape supply and recovery mechanism so that a substrate-side edge of the polishing tape makes contact with the contacting surface.
According to this configuration, since alignment of the polishing tape for allowing the polishing tape to be adsorbed to the pressing member is conducted according to a mechanical method of bringing the substrate-side edge of the polishing tape into contact with the contacting surface, it is possible to conduct alignment of the polishing tape without using an optical sensor in alignment of the polishing tape. Here, the radial direction of the substrate is a radial direction of the substrate at a polishing position when the edge portion of the substrate is polished by the polishing tape.
In the polishing apparatus, the pressing member may adsorb the polishing tape being in contact with the contacting surface. With this configuration, since the polishing tape being aligned in a state of being in contact with the contacting surface is adsorbed by the pressing member, it is possible to conduct alignment between the polishing tape and the pressing member with high accuracy.
In the polishing apparatus, a substrate-side edge of the pressing member and the substrate-side edge of the polishing tape may be aligned by moving the polishing head so that the substrate-side edge of the pressing member makes contact with the contacting surface. With this configuration, alignment can be conducted so that the substrate-side edges of the pressing member and the polishing tape are aligned.
In the polishing apparatus, the positioning unit may further include a position sensor having a distal end that protrudes from the contacting surface of the positioning block and is configured to detect an amount of protrusion of the distal end, and the first moving mechanism may move the polishing head to press the distal end of the position sensor with the substrate-side edge of the pressing member to thereby conduct alignment of the pressing member based on the detected amount of protrusion. With this configuration, alignment between the polishing tape and the pressing member can be conducted by setting the position of the pressing member in relation to the polishing tape in the radial direction of the substrate in an arbitrary manner.
In the polishing apparatus, the positioning unit may further include a third moving mechanism configured to move the positioning block in the radial direction of the substrate, and the third moving mechanism may move the positioning block so that the contacting surface coincides with an inner edge of the edge portion of the substrate. With this configuration, by realizing alignment of the polishing tape and/or the pressing member, the alignment of the polishing tape and/or the pressing member in the radial direction of the substrate can be also conducted.
The polishing apparatus may further include a polishing-unit moving mechanism configured to move the polishing unit in a tangential direction of the substrate. With this configuration, after the alignment of the polishing tape and/or the pressing member in the radial direction of the substrate is conducted at the tape alignment position, the polishing unit can be moved to the polishing position. Here, the tangential direction of the substrate is a tangential direction of the substrate at a polishing position when the edge portion of the substrate is polished by the polishing tape.
According to an embodiment, there is provided a polishing method including: rotating a substrate; aligning a polishing tape by bringing a substrate-side edge of the polishing tape into contact with a contacting surface; allowing the aligned polishing tape to be adsorbed on a pressing member; and pressing the polishing tape against a peripheral portion of the substrate using the pressing member to thereby polish the peripheral portion of the substrate. With this configuration, since alignment of the polishing tape for allowing the polishing tape to be adsorbed to the pressing member is conducted according to a mechanical method of bringing the polishing tape into contact with the contacting surface, it is possible to conduct alignment of the polishing tape without using an optical sensor in alignment of the polishing tape.
In the polishing method, the pressing member may adsorb the polishing tape being in contact with the contacting surface. With this configuration, since the polishing tape being aligned in a state of being in contact with the contacting surface is adsorbed by the pressing member, it is possible to conduct alignment between the polishing tape and the pressing member with high accuracy.
In the polishing method, after adsorbing the polishing tape, the pressing member may move to a polishing position in a state of adsorbing the polishing tape to polish the peripheral portion of the substrate at the polishing position. With this configuration, the polishing tape can be adsorbed to the pressing member at a position different from the polishing position.
In the polishing method, the pressing member may be aligned by bringing a substrate-side edge of the pressing member into contact with the contacting surface, and the pressing member may adsorb the polishing tape in a state of being in contact with the contacting surface. With this configuration, since alignment is conducted by bringing the polishing tape and the pressing member into the same contacting surface, the substrate-side edges of the polishing tape and the pressing member can be aligned.
In the polishing method, a position of the pressing member may be detected using a position sensor and the pressing member may be aligned based on a detection value of the position sensor, and the pressing member may adsorb the polishing tape at the aligned position. With this configuration, the polishing tape and the pressing member when the pressing member adsorbs the polishing tape may be in an optional positional relation.
In the polishing method, the pressing member may adsorb the polishing tape in such a positional relation that the substrate-side edge of the polishing tape is shifted closer to the substrate than the substrate-side edge of the pressing member. With this configuration, a tape allowance of the polishing tape is secured.